This invention relates to an apparatus and method for dispensing predetermined amounts of liquid by weight into a container and, in particular, is directed toward an improved apparatus and method for dispensing liquid into a container of the type shown in U.S. Pat. No. 4,211,263, which patent is hereby incorporated by reference. U.S. Pat. No. 4,211,263, which patent issued to the assignee of the present application, provides background information for the present invention.
In most facilities adapted for the filling of liquids into containers, the containers to be filled are conveyed by a suitable roller conveyor or like apparatus past a number of stations at which particular functions related to the filling of the container occur. For example, the empty containers are usually introduced singly onto the conveyor and may be carried past a first station whereat the liquid-receiving opening of each container is aligned or oriented into a predetermined position. The containers might also be oriented at the filling station. At the filling station, a predetermined quantity of liquid is introduced into the container.
Depending upon the nature of the liquid, any of several filling techniques may be utilized to dispense the predetermined metered amount of liquid into the container. If the liquid is susceptible to foaming, it is typically the practice to insert a filling lance (the conduit through which the liquid passes into the container) into the container such that the lower, discharge end of the lance is in close proximity to the bottom of the container. The movement of the filling lance is normally initiated by the operator of the filling apparatus. A predetermined small amount of liquid is then slowly introduced into the container until the level of liquid in the container rises above the discharge end of the lance. Since the discharge of the lance is thereafter below the level of liquid in the container, most of the remaining weight of the liquid may be introduced into the container at a relatively faster fill rate until the fill rate is slowed down (to a dribble fill rate) just before the final weight of liquid has been dispensed. During the fast fill operation, the lance is normally withdrawn from the container but at a rate which maintains the end of the lance below the liquid surface in the container. The withdrawal of the lance is generally controlled by the operator in order to maintain the discharge end of the lance subsurface.
Once the predetermined amount of liquid has been introduced into the container, the lance is fully withdrawn. As noted, for subsurface fill operations, a problem has existed in that the operations of liquid filling apparatus have had to control the withdrawal of the lance during the fill, keeping the lance subsurface to avoid foaming and the like and yet sufficiently withdrawn that the accuracy of the weight of liquid introduced was not significantly influenced by the weight of liquid within the lance. Further concern existed for the operators when working with toxic or noxious liquids, as it was desired to keep a minimum of the outside surface area of the lance from contamination by submergence in the liquid. As disclosed in the incorporated reference, U.S. Pat. No. 4,211,263, a wiper ring may be utilized about the lance to help alleviate this latter problem. In addition to the strain placed on operators to carefully monitor and control the lance withdrawal, it is believed that some inaccuracy in the final fill weight tends to occur because operators will withdraw the lance slower than necessary to avoid breaking the surface of the liquid.
Upon completion of the fill, the container will normally be conveyed along the line to another station where the container is capped.
It is believed advantageous to provide a liquid filling device that automatically controls the movement of the filling lance at the various stages in the filling process and, in particular, the withdrawal of the lance during a subsurface fill operation. It is also believed to be advantageous to provide a means for controlling fumes and excess material in a safe and efficient manner. It is further believed to be advantageous to provide a liquid filling apparatus which is of relatively simple construction and comprised of components easily maintained and operated, such an arrangement enhancing the safety and control of filling apparatus used with hazardous liquids.
The present invention may be used to make an improved liquid filling lance for U.S. Pat. No. 4,211,263, the incorporated reference.